Patent GB-794006-A (GB)
Title: Continuous purification of liquids
IPC: B01D21/00
Filed: 1956-11-02
Abstract: 794,006. Separating solids from liquids by gravity: filtering. DORR-OLIVER, Inc. Nov. 2, 1956 [Nov. 2, 1955], No. 33472/56. Class 46. In a method and/or apparatus for pretreating and filtering water or other liquid and comprising a pre-treatment zone and two or more adjacent filtering zones, a filtering zone is adapted to be isolated for cleaning without affecting the other filtering zone or zones by lowering the level of the water &c. in the pretreatment zone to interrupt the general flow to the filter beds and then opening a path or paths at a lower level from the pre-treatment zone to the filter zone or zones which are being kept in operation. The apparatus comprises a circular pre-treatment zone 48 surrounded by a zone contained between the wall 49 of the zone 48 and an outer wall 40, this zone being divided into inner and outer annular zones 50, 52 providing semi-annular gullets 50, 50<SP>1</SP> for wash water and similar chambers containing sand filters 53, 53<SP>1</SP> supported by porous beds 54, 54<SP>1</SP>. Radial partitions 80, 81 define these semiannular spaces or segments, The partition 51, 51<SP>1</SP> between the gullets 50, 51<SP>1</SP> and filter chamber 52, 52<SP>1</SP> is of less height than the partition wall 49. A launder or channel 63 is provided within the upper part of the wall 49 and communicates with the surrounding zones through openings 62, 621 controlled by doors 60, 60<SP>1</SP>, the doors being disposed in different segments of the outer zones. Liquid to be treated flows to an inlet pipe 42 under control of a valve 43 actuated pneumatically by a liquid level controller 71 adapted to maintain according to its setting one or other of two levels of liquid in the zone 48. After traversing a riser 39 the liquid is evenly delivered by a rotating arm 45 and rises up the central zone while part of the solids carried by it flocculate and sink to the floor 41 of the apparatus where scrapers 47 on the arm 45 transfer them to a sludge sump 76 for removal by a pipe 77, the removal being aided by scrapers 82 in the sump. Chemicals may be added to the liquid through a pipe 79. The pre-treated liquid rises to a high level WL-1 and overflows the wall 49 to descend on to the filter beds 53, 53<SP>1</SP> whence pipes 56, 56<SP>1</SP> deliver it from the apparatus. When a filter bed has to be cleared, e.g., the bed 53<SP>1</SP>, the level controller 71 is set for a lower level situated below the top of the wall 49 and above the wall 64 of the launder 63. The door 60 leading to the filter 53 to be kept in operation is opened and when the water level has fallen below the top of the wall 49 and no more water flows into the bed 53<SP>1</SP> to be cleaned its delivery pipe 56<SP>1</SP> is closed, a backwash pipe 66<SP>1</SP>, leading to a chamber 55<SP>1</SP> beneath the filter bed 53<SP>1</SP>, is opened together with a drain pipe 68<SP>1</SP> from the gullet 51<SP>1</SP> to provide an outlet for the backwash water. When cleaning is completed, the backwash and drain pipes are closed and the level controller re-set. The water level rises until the water overflows the wall 49 and reaches the cleaned filter bed. The door 60 is closed and a pipe 82<SP>1</SP> branched from the delivery pipe 56<SP>1</SP> is opened to clear the residual backwash water before the delivery pipe itself is opened.